President Obama arrived in Colombia for the Summit of the Americas yesterday, but the Secret Service agents sent in advance of his arrival were M.I.A. That's because 12 agents were relieved of duty and sent home after allegations of misconduct involving prostitution. Former Washington Post reporter Ronald Kessler calls it "clearly the biggest scandal in Secret Service history."

Kessler became aware of the investigation into Secret Service misconduct and alerted the Washington Post, which was the first publication to report on the story. According to Kessler, "One of the agents did not pay one of the prostitutes, and she complained to the police."

Agency spokesman Edwin Donovan released a statement in which he confirmed the allegations of misconduct against Secret Service agents but refused to elaborate on what exactly that misconduct entailed.

There have been allegations of misconduct made against the Secret Service in Cartagena, Colombia, prior to the president's trip. Because of this, those personnel are being relieved of their assignments, returned to their place of duty, and are being replaced by other Secret Service personnel. The Secret Service takes all allegations of misconduct seriously.

Federal Law Enforcement Officers Association President Jon Adler claims that at least one Secret Service agent was involved with a prostitute. This is the story Kessler is telling as well — the other 11 agents are accused of being complicit "in one degree or another."

President Obama's Colombia trip will be the most time any U.S. president has spent in the country due to security concerns. It follows, then, that the relieved Secret Service agents were quickly replaced.